What is this lung pain i have?

this is a long story, i can remember back when i was 9 or 10 i would have rare stabbing pains in my lung/ chest area my mom would say they were growing pains it subdued as i got older. it started back again about 5 years ago now im 32 yo and an ex smoker the pain in my lungs is strange. i've checked out many websites and have seen my doctor several times about it. he has x-rayed me and nothing shows up. its a sharp pain that moves from lung to lung, sometimes its higher in the lung sometimes lower but it is always there somewhere. its not always when i breath deep but when i exhale deep it is worse. im totally obsessed with it being lung cancer that i think i'll will myself to it. but none of my symptoms match cancer's symptoms. any help would be great.